1. Field of the Invention
The present invention relates generally to a drive train for use with a kneader apparatus and, more specifically, to an improved bearing assembly for supporting a portion of the drive train.
2. Description of the Related Art
Kneaders or mixing machines are typically used to knead, mix or compound a polymeric material. Typically, such machines include a mixing chamber. Inserted into the mixing chamber is a shaft or screw member that both rotates and reciprocates to mix material contained or placed within the mixing chamber. A gearbox houses a drive train used to power or drive the shaft or screw member. The drive train receives a rotational input, typically from an electric motor, and translates that rotary input into a rotary and reciprocal output. Accordingly, the shaft or screw member is coupled to the output of the gearbox.
One type of drive system used to impart axial motion to the shaft or screw member includes providing an eccentric on the output shaft. A pivot arm is pivotally attached within the gearbox and attaches to the eccentric on the output shaft. As the pivot arm is fixed at a discrete pivot point, when the output shaft rotates, the eccentric causes the output shaft to reciprocate back and forth along the longitudinal axis of the output shaft.
One manner of supporting the pivot arm within the gearbox is the use of a spherical plain bearing. However, such bearings are limited by contact pressure (p) and sliding the velocity (v); i.e., the amount of load the bearing can support and how fast the bearing surfaces move.
For spherical plain bearings constructed with both sliding contact surfaces of hardened steel, the recommended contact pressure (p) range is 1 N/mm2 to 100 N/mm2 and the recommended sliding velocity range (v) is 1 mm/sec to 100 mm/sec. However, the product of the contact pressure (p) and sliding velocity (v), the pressure velocity (p xc2x7v) value has a recommended range of 1N/mm2xc2x7mm/sec to 400 N/mm2xc2x7mm/sec. Therefore, spherical plain bearings are suitable for high contact pressure (p) at low sliding velocity (v) or low contact pressure (p) at high sliding velocity(v). Thus there remains a need in the art for a drive train capable of driving the output shaft at high rotation speeds and corresponding rapid reciprocation with a high degree of mechanical reliability.
The present invention is a drive train for use with a kneader apparatus. The drive train includes an input shaft rotatably supported in a housing. An output shaft is supported by the housing for rotational and axial movement. A pivot arm is pivotally attached on one end to the housing and engages the output shaft at the opposite end. Upon rotation of the output shaft, the pivot arm operates to drive the output shaft in a reciprocating manner. The reciprocal motion is in addition to the rotating motion. The pivot arm is pivotally supported on the housing by a first bearing assembly and a second bearing assembly. The first bearing assembly engages the pivot arm and the second bearing assembly engages the housing. A bearing shaft is disposed between and engages the first and second bearing assemblies. The bearing shaft is operative to drive the bearing assemblies.
One advantage of driving the bearing assemblies is that it rotates the bearings and correspondingly provides uniform distribution of load on the bearings and along with hydrodynamic lubrication to ensure smooth and efficient operation of the kneader. Accordingly, the present invention provides a kneader that operates at higher speeds and thereby increases the output of the kneader.